The most common currently used refrigerants have been chlorine-containing fluorocarbons (CFCs), such as CFC-11, CFC-12, CFC-114, and CFC-115. The presence of chlorine in these compounds causes them, once released into the atmosphere, to deplete the Earth's stratospheric ozone layer. As a result of their harmful effects, the use of CFCs is being phased out of production. For example, in the United States, the diminished use of CFCs is mandated by the Montreal Protocol, a multi-national agreement to which the United States is a party; the terms of this treaty were codified by the Clean Air Act of 1990.
Research has focused on alternative non-chlorinated refrigerants. The physical characteristics of a ideal refrigerant include low boiling point, low or non-flammability, high thermal stability, high chemical stability with other compounds to which it is exposed, low toxicity, and high energy efficiency. Suggested alternatives to CFCs have included hydrofluoroethers (HFEs), see Eiseman, Jr., U.S. Pat. No. 3,362,180; O'Neill et al., U.S. Pat. No. 4,961,321; Powell, U.S. Pat. No. 4,559,154; hydrofluorocarbons (HFCs), see Walters, U.S. Pat. No. 4,157,979; Japanese Patent No. 2272-186; azeotropic mixtures of HFEs and HFCs with CFCs and hydrochlorofluorocarbons (HCFCs), see Fellows et al., U.S. Pat. No. 4,948,526; Murphy et al., U.S. Pat. No. 4,054,036; Snider et al., U.S. Pat. No. 3,536,627; Eiseman, Jr., U.S. Pat. No. 3,409,555 (although HCFCs are also being phased out by the 1990 Clean Air Act); and isolated azeotropic mixtures, see Eiseman, U.S. Pat. No. 3,394,878 (mixture of trifluoromethyl methyl ether and trifluoromethyl pentafluoroethyl ether); Shankland et al., U.S. Pat. No. 4,978,467 (mixture of pentafluoroethane and difluoromethane); Hutchinson, U.S. Pat. No. 3,922,228 (mixture of difluoromethyl trifluoromethylether and dimethyl ether).
These alternative refrigerants represent a wide range of boiling points; nevertheless, suitable replacements do not exist for all CFC and HCFC refrigerants. Problems researchers have encountered include the difficulty of manufacturing these refrigerants and the lower energy efficiency associated with many of them. Accordingly, new refrigerants that satisfy specific refrigeration requirements are always desirable. Corresponding processes that can fully capitalize on the properties of new refrigerants are also desirable.